#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;
const int N = 500010;
int n;
long double s;
int a[N];

int main()
{
    cin >> n >> s;
    for(int i = 0; i < n; ++i) cin >> a[i];
    long double avg = s / n;
    long double res = 0;
    sort(a, a + n);
    for(int i = 0; i < n; ++i)
    {
        long double cur = s / (n - i);
        if(a[i] < cur) cur = a[i];
        res += (cur - avg) * (cur - avg);
        s -= cur;
    }
    printf("%.4Lf", sqrt(res / n));
    return 0;
}